docs: def get_executing_jobs(db):
      """
      :param db:
          a :class:`openquake.server.dbapi.Db` instance
      :returns:
          (id, pid, user_name, start_time) tuples
      """
      fields = 'id,pid,user_name,start_time'
      running = List()
      running._fields = fields.split(',')
  
      query = ('''-- executing jobs
  SELECT %s FROM job WHERE status='executing' ORDER BY id desc''' % fields)
      rows = db(query)
      for r in rows:
          # if r.pid is 0 it means that such information
          # is not available in the database
          if r.pid and psutil.pid_exists(r.pid):
              running.append(r)
      return running